1. Field of the Invention
This invention relates to a method of and apparatus for determining optical quality of an article.
2. Discussion of the Prior Art and Technical Problems
In the manufacture of laminated articles, e.g. automotive windshields it is desirable to know the quantitative value of the final optical performance of the laminate components prior to making the laminate. For example, to know or predict the optical performance of the interlayer material after lamination by inspecting the interlayer material prior to lamination. The prior art teaches that optical power value of glass plates are determined prior to lamination to determine if optically acceptable laminates can be made therefrom. More particularly, U.S. Pat. No. 3,639,112 teaches a distortion analyzer for scanning a glass ribbon and producing a trace proportional to the second derivative of glass thickness with respect to distance traversed. Windshield blanks are cut from sections of the glass ribbon where the second derivative has a minimal value. A limitation of the above technique is that it does not consider the optical contribution of the interlayer material which is laminated between the windshield blanks. The optical performance of the interlayer material should be known when it is realized that advances in glass technology have made it possible to produce glass ribbons that are substantially flat making the optical contribution of the interlayer material more predominant.
It would be advantageous therefore to provide a method of and apparatus for determining optical quality of an interlayer material prior to and after lamination by inspecting the interlayer material prior to lamination.